Yes Ari had 3 kids in season one but it was changed to 2. Its a comedy show so small omissions like this the disapperance of arnold, Vince - Drama family relationship (brother / half brother), Ari cheating, claiming to have siblings one time then denies it annother, can be overloked! Maybe it was Ari nephew and he just lived with him for season 1!

k so i read in the behind the scenes book, that they have three children two daughters and a son, as we can see in the bat mitzvah episode, but Perrey Reeves says that only two children have names, so they kindive just only show those two, Sarah and Jonah. But in the show there are alot of mistakes like Ari said he didn't have any sisters and than he said he does, so you never know!